The objective of this proposal is to study the control of cyclic AMP levels in cells. Included will be: (1) measurements of cyclic AMP changes in intact cells in response to hormones and other agents; (2) studies with purified preparations of adenyl cyclase from several tissues; and (3) studies with purified preparations of the cyclic nucleotide phosphodiesterase. It is hoped that these studies will lead to a clearer understanding of mammalian control systems and the integration of cellular processes. If such understanding is obtained it may be of great value in human medicine in the treatment of endocrinopathies and perhaps in other diseases involving faulty control processes.